Yesterday, I solved a recurring false alarm caused by a swinging ceiling fan. | Alarm System Installers

Eric Brown · 2026-03-04T17:06:15.414495+00:00

Turns out, the fan's shadow was tripping the infrared sensor.

Last year, I fixed a false alarm where the fan's vibration was the real issue. PIR sensors are made to detect heat, so a shadow shouldn't set them off on its own. The problem could be from the fan moving air around, not just the shadow.

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jesse_white197mo ago

Read that shadows can trick PIR sensors by changing local heat.

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the_lucas7mo ago

My friend had a similar issue. His motion sensor kept getting set off by a shadow from a spinning ceiling fan.

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